Natural infection of maize by Pennisetum mosaic virus in China

In mid-2002, a potyvirus was isolated from maize (Zea mays) showing mild mosaic symptoms in the Xinzhou District of Shanxi Province, China. This isolate was mechanically transmitted to maize (cultivar Ye-Dan No.2) and Sorghum bicolour (4 cultivars: Atlas, Xin-Liang Nos. 7 and 52, and Xiong-Yue 191). All inoculated plants developed systemic mosaic symptom. In serological tests, the virus was distantly related to Sugarcane mosaic virus (SCMV); the prevalent potyvirus infecting maize across China (Fan et al., 2003a), but closely related to the newly identified Pennisetum mosaic virus (PenMV) isolated from a perennial grass (Pennisetum centrasiaticum) (Fan et al., 2003b).

The nucleotide sequence of the putative coat protein (CP) gene of the virus isolated has been determined (accession number AY543166) and comprising 909 nucleotides, encoding 302 amino acid residues. Sequence comparisons amongst all potyviruses reported to date showed that this isolate was most closely related to PenMV (accession number AY172336) (Fan et al., 2003b). The sequence identity between the putative CP genes of the maize isolate and PenMV was 92%, while between the CPs it was 99% at the amino acid level, thus identifying the virus isolated from maize as PenMV.

This is the first report of PenMV in maize, where before SCMV had been the only potyvirus infecting maize in China. SCMV occurs in most maize-growing areas of China, and its symptoms, on most cultivars of sorghum, are mosaic followed by reddening and necrosis of the lamina. In contrast the distribution of PenMV appears limited, as maize from only one region of China has been found to be infected and the symptoms it caused, especially on sorghum, were significantly milder when compared to those of SCMV.